Cellulose acetate.



NITED' STATES ATENT OFFICE.

ARTHUR EIOHENGRI TN AND THEODOR BECKER, OF ELBERFELD, GERMANY, ASSIGNORSTO FARBENFABRIKEN OF ELBERFELD OO., OF NEW YORK, N. Y., A CORPORATION OFNEW YORK.

CELLULOSE ACETATE.

Specification of Letters Patent.

Patented Jan. 16, 1906.

Application filed February 20, 1903. Serial No. 144,338. (Specimens) Toall whom, it 11mg concern.-

Be it known that we, ARTHUR EIOHEN- GRi'IN and THEODOR BECKER, doctorsof philosophy, chemists, residing at Elberfeld, Germany, (assignors tothe FARBENFABRIKEN OF ELBERFELD 00., of New York,) have invented a newand useful Improvement in Cellulose Acetate and we hereby declare thefollowing to be a clear and exact description of our invention.

In the specification of our application for Letters Patent, Serial No.88,898, filed the 8th of January, 1902, we have described a newacetylized derivative of cellulose, being a triacetyl cellulose, whichwe prepare by treating cellulose with acetic anhydrid and sulfuric acid.In the further course of experiments we have found that this reactiontakes place in two phases. At first an acetate is produced which issoluble in alcohol, this product being then transformed by the furtheraction of acetic anhydrid and sulfuric acid into the above-mentionedtriacetyl cellulose insoluble in alcohol. e have now succeeded incarrying out the action of acetic anhydrid and sulfuric acid oncellulose in such a way as the above-mentioned acetate, soluble inalcohol, is prepared as chief product. For this purpose we stop theprocess when the body soluble in alcohol at first produced begins to betransformed into the triacetyl cellulose insoluble in alcohol.

In carrying out this process practically we can proceed as follows, theparts being by weight: A mixture of eighty parts of acetic anhydrid,eighty parts of glacial acetic acid, four parts of concentrated sulfuricacid, and twenty parts of cellulose (e. g., cotton-yarn) is allowed tostand at from 20 to 25 centigrade, with stirring from time to time.After about ten hours the whole mass is transformed into a thick syrup.WVhen the precipitate obtained by diluting a test portion with watercontains only a small quantity of unchanged particles of cellulose andis still soluble in hot alcohol, the production of the new celluloseacetate is completed. The reaction mass is then mixed with a largequantity of water by stirring, and the precipitate thus obtained isfiltered oh and pressed. The new body thus obtained is solid and cantake various forms, according to the way in which it is prepared. In awet state it is a whitish voluminous mass. hen dry, it representsyellowish hard lumps. It can also be obtained in transparent sheets andfilms by evaporation of its solutions. It is soluble in a seventy percent. hot alcohol, the alcoholic solution solidifying to a gelatinousmass on cooling. By the addition of much water to the alcoholic solutionthe new cellulose ester is precipitated in fine light flakes.

Having now described our invention and in what manner the same is to beperformed, what we claim as new, and desire to secure by Letters Patent,is

The herein-described new cellulose acetate, characterized by being aderivative of cellulose, being soluble in hot alcohol of seventy ercent. and being produced by treating celulose with a mixture of aceticanhydrid and sulfuric acid which is in a wet state a whitish voluminousmass and represents when dry yellowish hard lumps, the acetate beingprecipitated therefrom by the addition of much water in the shape ofline light flakes the alcoholic solution solidifying in the cold to agelatinous mass and being capable of forming transparent flexible sheetsand films by evaporation of its solutions, substantially as hereinbeforedescribed.

In testimony whereof we have signed our names in the presence of twosubscribing witnesses.

ARTHUR EICHENGRUN. THEODOR BECKER.

Witnesses O'r'ro KONIG, J. A. Rrrrnnsrmus.

